#! /usr/bin/python
# coding: utf-8

from Tkinter import *

root = Tk()

e = StringVar()
e.set('input your text here')

def validateText(contents):
    if not contents:
        return True
    else:
        return False

entry = Entry(root, validate='key', textvariable=e)
entry.configure(validatecommand=validateText)
entry.pack()

root.mainloop()
